Like Pearlie says you might not notice a difference. As you are tillering don't try to compare the thickness of the two limbs. Just tiller the bow until both limbs bend evenly and together. I'm curious to see how it works out.
I have seen a bow with 2 different woods, one limb osage and one yew. There is a big difference between the two woods but the bow shot well without and noticable difference.